Hi,I have a rectangular concrete pool that is tiled and that has thin cracks that let water out and in. I have had quotes to reline my pool with 2 solutions either a reinforced PVC liner or a sprayed on fiberglass membrane then coated with gel coat. The prices are very similar. I can not afford to re-build and re-tile the pool. My fear is that the pool, which is 30 years old, may continue to move and crack, if I use fiberglass will it also crack and if water gets under the fiberglass will it affect it? If I use the PVC liner and the concrete structure is unstable might it collapse?Can anyone recommend which method would be better please.Thanks